Songqi Ma

Bio-based epoxy resin from itaconic acid and its thermosets cured with anhydride and comonomers

A novel itaconic acid (IA) based epoxy resin with curable double bonds (EIA) was synthesized by the esterification reaction between IA and epichlorohydrin (ECH). Its chemical structure was confirmed in detail by FT-IR, 1H-NMR and ESI-ION TRAP MS before being cured by methyl hexahydrophthalic anhydride (MHHPA). In order to manipulate the properties of the cured resin, divinyl benzene (DVB) and acrylated epoxidized soybean oil (AESO) were employed here to act as comonomers. The results demonstrated that EIA showed a higher epoxy value of 0.625 and higher curing reactivity toward MHHPA compared with the commonly used diglycidyl ether of bisphenol A (DGEBA). The glass transition temperature, tensile strength, flexural strength and modulus of the cured EIA without comonomers were 130.4 °C, 87.5 MPa, 152.4 MPa and 3400 MPa, respectively, which were comparable or better than those of DGEBA cured by the same curing agent. After being copolymerized with DVB or AESO, the properties of the cured EIA could be regulated further. The results indicated that EIA has great potential to replace the petroleum-based thermosetting resin, such as DGEBA.

The properties of poly(lactic acid)/starch blends with a functionalized plant oil: tung oil anhydride.

Bio-sourced polymers, polylactide (PLA) and starch, have been melt-blended by lab-scale co-extruder with tung oil anhydride (TOA) as the plasticizer. The ready reaction between the maleic anhydride on TOA and the hydroxyl on starch led TOA molecules to accumulate on starch and increased the compatibility of PLA/starch blends, which was confirmed by FT-IR analyses and SEM. The TOA could change the mechanical properties and physical behaviors of PLA/starch blends. DSC and DMA analysis show that the TOA layer on starch has an effect on the thermal behavior of PLA in the ternary blend. The enrichment of TOA on starch improves the toughness and impact strength of the PLA/starch blends. The adding amount of TOA in PLA/starch blends primarily determined the compatibility and mechanical properties of the resulted ternary blends. The tensile and impact fracture modes of the PLA/starch blend with or without TOA has also been investigated by SEM analysis.

Polyesters derived from itaconic acid for the properties and bio-based content enhancement of soybean oil-based thermosets

A series of bio-based polyesters were synthesized by melt polycondensation of itaconic acid with diols and glycerol without VOC emission. Their chemical structures were confirmed by FT-IR and 1H-NMR before they were made to copolymerize with acrylated epoxidized soybean oil (AESO). The thermal and mechanical properties of the resulting thermosets were investigated by differential scanning calorimetry (DSC), tensile testing and dynamic mechanical analysis (DMA). Their coating properties on tinplate and glass plate were also studied. Results showed that the tensile strength, modulus, glass transition temperatures and bio-based content of the AESO-based thermosetting resins were significantly improved after the introduction of the synthesized polyesters. In addition, the modified AESO systems could be well coated on the surface of tinplate and glass plate and good coating properties such as hardness, flexibility, adhesion, solvent resistance and water absorption were demonstrated. They showed great potential for applications as coatings, adhesives and composites.

Effect of castor oil enrichment layer produced by reaction on the properties of PLA/HDI-g-starch blends

Blends of entirely bio-sourced polymers, namely polylactide (PLA) and starch, have been melt-compounded by lab-scale co-extruder with castor oil (CO) as a plasticizer. The enrichment of castor oil on starch had great effect on the properties of the blends. If the castor oil was mainly dispersed in PLA matrix, the properties of the blends were poor, but when the hexamethylenediisocyanate (HDI) was grafted on starch granules the ready reactions between the hydroxyl on CO and the isocyante on the HDI-grafted starch (HGSTs) brought CO molecules enriched on starch particles. DSC analysis shows that the CO layer on starch has a positive effect on the crystallization of PLA in the ternary blend. The accumulation of CO on starch greatly improves the toughness and impact strength of PLA/starch blends. The grafting content of HDI on the starch granules primarily determined the compatibility and properties of the resulted blends.

Bio-based tetrafunctional crosslink agent from gallic acid and its enhanced soybean oil-based UV-cured coatings with high performance

The utilization of soybean oil-based UV coatings depends on the introduction of petroleum-based comonomers or crosslink agents. Thus, in this paper, a bio-based crosslink agent (GACA) for UV curable coatings was synthesized from gallic acid and its chemical structure was confirmed by FT IR, 1H NMR and 13C NMR. Crosslinked networks with high biobased content of more than 88% were obtained after co-photopolymerization between acrylated epoxidized soybean oil (AESO) and GACA. The thermal, mechanical and coating properties of these GACA crosslinked AESO networks were investigated and a commonly used crosslink agent triallyl isocyanurate (TAIC) was used as the control. GACA exhibited more functional groups and better copolymerization with AESO than TAIC, resulting in the higher gel content, crosslink density, tensile strength and modulus as well as much better coating properties (reflected by the higher pencil hardness, better wear resistance and adhesion) of GACA crosslinked AESO networks than TAIC crosslinked AESO networks. These results indicated that GACA exhibited great potential to replace petroleum-based crosslink agents such as TAIC, and high-performance soybean oil-based UV-cured coatings with high biobased content could be achieved after introducing GACA.

Cycloaliphatic epoxy resin modified by two kinds of oligo-fluorosiloxanes for potential application in light-emitting diode (LED) encapsulation

Oligo-fluorosiloxane (DFOS) and epoxy-containing oligo-fluorosiloxane (DFEHOS) were synthesized by the hydrolytic condensation reaction to modify 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexanecarboxylate (ERL-4221) for potential application in LED packaging. The chemical structures of DFOS and DFEHOS were characterized by Fourier transform infrared (FT-IR), 29Si nuclear magnetic resonance (29Si NMR), and gel permeation chromatography (GPC). The thermal behavior, mechanical properties, morphologies of impact fracture surfaces, surface wettability and absorbency of the modified epoxy resins were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile and impact testing, scanning electron microscopy (SEM), and contact angle measurement, respectively. The experimental results indicated that the contact angles, surface energies and water absorption ratios of the modified epoxy resins were effectively improved by the introduction of oligo-fluorosiloxanes. Compared to neat epoxy resin, the thermal stabilities of DFEHOS-modified epoxy resins were basically kept, and that of DFOS-modified epoxy resins were slightly depressed with the increasing content of modifiers. As the additive quantity of modifiers was about 5pph to 15pph relative to ERL-4221, good thermal stability, fracture toughness and surface hydrophobicity of the modified epoxy resin was exhibited, and the cured DFEHOS-10 that embraced the relatively optimum comprehensive property was possible for LED encapsulation. Moreover, the reactable groups formed during hydrolytic condensation in DFOS and DFEHOS made good compatibilities between the modifiers and the epoxy matrix.

Origin of highly recoverable shape memory polyurethanes (SMPUs) with non-planar ring structures: a single molecule force spectroscopy investigation

In this work, SMPUs with non-planar ring structures in the hard segments display a low degree of phase separation but excellent shape recoverability (shape recovery rate ∼99% with 500% strain). The accepted wisdom is that there are two criteria for SMPUs possessing good shape recoverability: (i) high degree of phase separation forming physical crosslinks; (ii) strong physical interactions between hard segments which keep physical crosslinks stable under external stress. However, our results are completely against the accepted wisdom since the asymmetrical non-planar ring structures will depress the micro-phase separation and physical interactions in the hard phase. Thus, the excellent shape recovery could not be attributed to the phase morphology. Based on such results, single molecule force spectroscopy was adopted to study the properties of single polymer chains with non-planar ring structures. We found that the single chain elasticity was largely improved by non-planar rings. It is highly possible that the excellent shape recovery property originates from the elastic non-planar ring structures absorbing the external stress which stabilizes the physical crosslinks. Much work needs to be done in the near future to confirm this assumption.

Diisocyanate free and melt polycondensation preparation of bio-based unsaturated poly(ester-urethane)s and their properties as UV curable coating materials

This paper reported the synthesis of bio-based unsaturated poly(ester-urethane)s via a nonisocyanate route, by metal-catalyzed melt polycondensation of itaconic acid with urethanediols. Three novel types of bio-based unsaturated poly(ester-urethane)s, namely, poly(urethanediol 2-itaconic acid), poly(urethanediol 4-itaconic acid) and poly(urethanediol 6-itaconic acid) (poly(U2-IA), poly(U4-IA) and poly (U6-IA) for short code, respectively), were prepared by a green synthetic route. The urethane linkage was formed by the reaction of two equivalent of ethylene carbonate with 1,6-hexanediamine, 1,4-butanediamine and 1,2-ethanediamine to form urethanediols. The urethanediols underwent polymerization with itaconic acid (IA) in the presence of metal catalyst dibutyltin dilaurate (DBTL) to produce low-molecular-weight bio-based unsaturated polyurethanes. Then, these bio-based unsaturated poly(ester-urethane)s were formulated with free radical photoinitiator and curing promoter to prepare UV curable polyurethane systems. After UV curing, the tensile properties, thermal properties and general coating properties of the three UV-cured polyurethane films were similar to that of UV cured polyurethane films prepared by polyurethane-acrylate (PUA). The results suggested that the obtained bio-based unsaturated polyurethanes could serve as coating materials.

Studies on the Thermal Properties of Epoxy Resins Modified with Two Kinds of Silanes

Dimethyldiethoxysilane (DMDES) and diphenyldimethoxysilane (DPDMS)-containing epoxy resins were synthesized by dehydration polycondensation. The chemical structures were determined by FT-IR, 1H NMR, and 13C NMR. The cured samples, with 4, 4′-diaminodiphenylmethane (DDM) as curing agent, were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile and impact testing. Results showed that DMDES and DPDMS-modified epoxy resins possess higher glass transition temperatures, better thermal stability, and better fracture toughness than the neat epoxy resin.

Mechanical and Thermal Properties and Morphology of Epoxy Resins Modified by a Silicon Compound

A silicon compound (GAPSO) was synthesized to modify the diglycidyl ether of bisphenol-A (DGEBA). The chemical structure of GAPSO was confirmed using FT-IR, 29Si NMR and GPC. The mechanical and thermal properties and morphologies of the cured epoxy resins were investigated by impact testing, tensile testing, differential scanning calorimetry and environmental scanning electron microscopy. The impact strength and tensile strength were both increased by introducing GAPSO, meanwhile the glass transition temperature (Tg ) was not decreased and the morphologies of the fracture surfaces show that the compatibility of GAPSO with epoxy resin was very good and the toughening follows the pinning and crack tip bifurcation mechanism. The high functional groups in GAPSO can react during the curing process, and chemically participate in the crosslinking network. GAPSO is thus expected to improve the toughness of epoxy resin, meanwhile maintain the glass transition temperature.